This invention relates to seals, and more particularly to seals that are capable of pumping or impelling a lubricant back to the regions isolated by such seals and to such seals combined with a machine structure sealed thereby.
Front wheel drive automobiles have little space to spare in the regions of their front wheels, and as a consequence automobile manufacturers utilize highly compact bearings for the front wheels of their vehicles. Some manufacturers have turned to angular contact ball bearings by reason of the compact configurations which are available with such bearings, but these bearings do not have the load-carrying capacity nor the durability of tapered roller bearings, which are generally somewhat larger, particularly in the axial dimension. Indeed, double row tapered roller bearings have experienced wide spread use in front wheel drive automobiles. As with any bearing designed for road wheels, the double row tapered roller bearing requires a seal at each of its ends, and to keep the bearing as compact as possible, the seals are often fitted directly into ends of the cup or outer race such that they encircle and indeed contact the cone or inner race.
The typical front wheel bearing operates over a wide range of temperatures, and this variance is accompanied by a corresponding variance in pressure within the sealed interior of the bearing. With some seals, the live seal formed by it becomes more effective with the increase in temperature, but this is not necessarily desirable, because it may damage the seal, or in extreme cases may cause the seal to actually be dislodged from the cup in which it is normally retained. Thus, the sealed cavity should be vented, and various arrangements have been developed for achieving this end.